Transformers are utilized in many applications such as for changing the voltage of alternating current electricity. A transformer has one or more primary windings and one or more secondary windings. The primary winding(s) receives electrical energy, such as from a power source and couples this energy to the secondary winding (s) by means of a changing magnetic field. The energy appears as an electromagnetic force across the winding. Typical transformers are implemented using an arrangement of coils, such as may be arranged so as to be juxtaposed. Alternatively, the coils may be arranged so that one coil surrounds another coil. The extent to which magnetic field generated at one winding links the other winding is expressed in terms of the winding's coupling coefficient.
As one example, a transmitter's main RF power amplifier can be implemented as a plurality of parallel-connected RF amplifier modules, whose outputs are combined to produce a composite amplified signal. One or more transformers can be utilized to combine the power from power amplifiers to provide a corresponding aggregate output at a desired power. Demands in many fields, including wireless communications, have prompted design efforts to lower-cost solutions that exhibit the same or better performance but operate with reduced power consumption. The reduced power consumption is often is prompted by further requirements in lowering supply voltages to various integrated circuits. Accordingly, there is a continuing need to provide more efficient, low cost transformers and/or power combiner.